I have installed a new engine on my 2000 chevy blazer. The engine will not start.
The fuel pump is working properly and the spark plugs are getting fire.
Can some please give me some advise, of what could be the problem.
I also have went through the timing several times. 4.3L engine.

Same engine as the one that came out of it?
Was the engine running before you put it in this truck?
Is the ECU the same for both engines?
All the sensors hooked back up?

Same engine as the one that came out of it?
Was the engine running before you put it in this truck?
Is the ECU the same for both engines?
All the sensors hooked back up?

Yes the ECU is the same, and all of the sensors are hooked up.